Cardiac Stress Tests...

 Nuclear stress tests and stress echocardiograms look at thinning of cardiac muscle, which indicates arterial blockage, but they do not localize or visualize where the problem is.  There's no way to compare a nuclear stress test to a CT as far as I know because they look at different things.  Nuclear stress tests basically tell you if there's a problem, but it takes another test such as a CT coronary angiogram or cardiac catheterization to find exactly where the blockage is.